Gulls, often casually referred to as “seagulls,” are common around the world, scavenging at coastal piers or soaring over inland parking lots. Their global presence suggests their total population must be enormous. However, calculating a precise worldwide figure for this highly mobile group of animals is an immensely complicated task for ornithologists. This difficulty leads to population estimates that often carry a wide margin of error. Determining the number of gulls requires understanding the different species and how their lives complicate the counting process.
Defining the Term “Seagull”
The term “seagull” is a colloquial and non-scientific name, as no single species is officially designated as such. These familiar birds belong to the family Laridae, a diverse group that includes gulls, terns, and skimmers. The true gulls are classified within the subfamily Larinae, comprising approximately 50 distinct species globally. These species are widely distributed and adaptable, ranging from the tiny Little Gull to the massive Great Black-backed Gull. Scientists focus their population counts on these 50 gull species, rather than the entire Laridae family, which includes around 100 species.
Global Population Estimates and Data Limitations
Recent scientific models offer a glimpse into the colossal scale of the gull population. An analysis published in the Proceedings of the National Academy of Sciences estimated the global abundance of nearly 10,000 bird species using data from citizen science projects like eBird. This study revealed that at least two specific gull species number in the hundreds of millions of individuals. These figures suggest the total population of all 50 gull species likely exceeds several billion individuals.
The Ring-billed Gull, for example, was estimated to have a global population of around 1.2 billion individual birds, placing it among the most numerous bird species on Earth. Similarly, the Glaucous Gull was estimated to number nearly 949 million individuals worldwide.
This high level of imprecision stems from several factors, including the lack of centralized, simultaneous global surveys for all species. Population counts rely heavily on estimating the number of breeding pairs in colonies, which is difficult to standardize across different regions and habitats. Furthermore, the high mobility and long-distance migration patterns of many gull species complicate counting. Individuals counted in one location during a non-breeding season may represent a population from an entirely different region. Therefore, the total number is certainly in the billions, but the exact count remains an estimate with a substantial margin of error.
Methodology for Population Monitoring
Ornithologists employ a variety of techniques to monitor gull populations, focusing primarily on their breeding colonies. One common method is the direct count of “Apparently Occupied Nests” (AONs) or breeding pairs within a colony during the nesting season. This process is time-intensive, requiring trained observers to count nests with eggs or chicks, either by walking through the colony or observing from a vantage point.
For large or inaccessible colonies, such as those on remote cliffs or islands, scientists use remote sensing techniques. This involves aerial surveys using traditional aircraft or Unmanned Aerial Vehicles (UAVs) equipped with high-resolution cameras. These images are later analyzed to count nesting birds or occupied territories, though distinguishing between closely related species can be difficult.
Mark-recapture methods, which involve banding individual birds, also provide data on survival rates, movement, and population turnover. The challenge is magnified because gulls do not reach breeding age for several years, meaning colony counts only represent a fraction of the total population. Gulls often nest in dense, noisy, and remote environments, further complicating the logistics of obtaining a consistent and accurate census.
Regional Distribution and Conservation Status
Gulls have achieved a cosmopolitan distribution, breeding on every continent, including the margins of Antarctica, and demonstrating remarkable ecological flexibility. While many species are associated with coastal marine environments, their adaptability allows them to exploit inland habitats, including lakes, rivers, agricultural fields, and urban centers. Gull diversity is highest in the temperate latitudes of the Northern Hemisphere.
The conservation status of gulls is not uniform, presenting a complex picture of regional decline alongside overall abundance. While species like the Ring-billed Gull are numerous, many other well-known species are experiencing population stress. For example, the Herring Gull is classified as Red-listed in some regions due to long-term declines in its breeding and wintering populations.
Similarly, the Great Black-backed Gull has experienced steep declines in North America and Europe, leading to recommendations that its global IUCN Red List status be uplisted to ‘Vulnerable’. These localized declines are often linked to human activity, such as changes in fishing practices that reduce food availability or the closure of landfills, which were once an abundant food source. This mixed status highlights that even numerous species can face substantial threats and require specific conservation attention.